1. Field of the Invention
The present invention relates to a vacuum processing apparatus for treating an object in a vacuum, such as an etching apparatus, an ashing apparatus, an ion inplantation apparatus, or a sputtering apparatus.
2. Description of the Related Art
In conventional vacuum processing apparatuses, in general, an object to be processed is contained in a vacuum processing chamber, and a vacuum is created within the chamber. A given vacuum process is applied to the object in the vacuum atmosphere. Such vacuum processing apparatuses include, for example, an etching apparatus, an ashing apparatus, an ion injection apparatus, a sputtering apparatus and a vacuum CVD apparatus. In this type of vacuum processing apparatus, once the pressure within the vacuum processing chamber is restored to a normal pressure, it is necessary to create a vacuum once again to a predetermined pressure level, which requires a very long time. Thus, in order to raise a through-put of vacuum process, an auxiliary vacuum chamber having a smaller volume than the vacuum processing chamber is provided adjacent to the vacuum processing chamber, and the pressure within the auxiliary vacuum chamber alone is restored to a normal pressure level or a vacuum is created within the auxiliary vacuum chamber alone.
In the auxiliary vacuum chamber, however, there are reaction products due to etching with the vacuum process within the vacuum processing chamber, a transfer mechanism for transferring wafers between the auxiliary vacuum chamber and the vacuum processing chamber, and many particles produced by a driving mechanism, etc. Particles which have fallen within the chamber are dispersed by gas flows caused when the auxiliary vacuum chamber is evacuated to create a vacuum or nitrogen gas is supplied in the auxiliary vacuum chamber to restore the internal pressure to a normal pressure level. The dispersed particles adhere to semiconductor wafers and degrade the quality of the wafers, resulting in a decrease in yield.
In the prior art, a turbulent flow within the chamber is suppressed by supplying nitrogen gas slowly into the auxiliary vacuum chamber at the time of supplying nitrogen gas or by evacuating the chamber slowly ("slow evacuation" or "slow ventilation"), thereby preventing dispersion of particles as much as possible.
In the case of the conventional vacuum processing apparatus, however, the pressure within the auxiliary vacuum chamber is frequently changed from a normal pressure level to a vacuum pressure level, or vice versa. By the slow evacuation, a turbulent flow near an exhaust port can be suppressed and dispersion of micron-order particles can be prevented. However, dispersion of sub-micron-order or half-micron-order particles of, e.g. 1.0 to 0.03 .mu.m cannot be prevented by the slow evacuation or the like.
Accordingly, when a semiconductor device such as a 4MDRAM, which requires only micron-order fine processing, is manufactured, dispersion of particles can be sufficiently prevented by the slow evacuation of the conventional vacuum processing apparatus. In the case of manufacturing a semiconductor device of 16MRAM or a greater-capacity RAM, which requires submicron- or half-micron-order fine treatment, it is difficult to prevent dispersion of submicron- or half-micron-order particles with the conventional vacuum processing apparatus. Such submicron- or half-micron-order particles may adhere to the semiconductor wafer W, degrading the quality of the wafer and lowering the yield.